A wall 2 cm thick is to be constructed from material that has an average thermal conductivity of 1.3 W/m· ºC. The wall is to be insulated with material having an average thermal conductivity of 0.35 W/m· ºC, so that the heat loss per square meter will not exceed 1830W. Assuming that the inner and outer surface temperatures of the insulated wall are 1300 and 30ºC, calculate the thickness of insulation required.